JP7647591B2 - Exhaust purification system - Google Patents

Description

The present invention relates to an exhaust purification system that injects a reactive liquid into the exhaust pipe of an internal combustion engine, mixes it with the exhaust gas, and purifies the exhaust gas in an aftertreatment device.

Conventionally, when purifying exhaust gas from an internal combustion engine mounted on a vehicle, it is known that a reactive liquid is mixed with the exhaust gas and reacted in an aftertreatment device. To improve purification efficiency, it is desirable to uniformly disperse the reactive liquid in the exhaust gas before it flows into the aftertreatment device. Therefore, a technology is known in which, in order to disperse the reactive liquid, a dispersion member is provided upstream of the aftertreatment device and the reactive liquid is collided with the dispersion member to atomize and disperse it.

For example, Patent Document 1 discloses a dispersion plate with multiple blades on the inner peripheral surface of a cylinder. The multiple blades do not extend to the center of the cylinder, and as a result, a passage opening is formed that is surrounded by the tips of the multiple blades. The passage opening is covered by a shielding plate with which the reaction liquid collides in the dispersion plate. After colliding with the shielding plate, the reaction liquid sprayed toward the shielding plate further collides with the multiple blades and is uniformly dispersed in the exhaust gas.

The exhaust pipe upstream of the aftertreatment device extends straight up to the section where the dispersion member is located just before it connects to the aftertreatment device, but beyond that section it often curves due to the condition of the mounting space on the vehicle. In such cases, the addition valve that injects the reaction liquid toward the dispersion member must be installed on the outside of the curved exhaust pipe.

As a result, the reactive liquid that is sprayed toward the dispersion member and flies through the air is subjected to a force from the exhaust gas flowing through the curved exhaust pipe in a direction different from the direction of travel. As a result, the reactive liquid collides with a position on the dispersion member that is shifted from the intended position. Furthermore, because the flow rate of exhaust gas changes depending on the driving conditions, the magnitude of the force that the reactive liquid flies through the air is subjected to is not constant but constantly changes.

JP 2014-163232 A

In order to ensure that the reaction liquid collides with the dispersion member, it is not enough to simply set the injection direction of the addition valve to an optimal value; the size of the dispersion member must be set large, taking into consideration the extent to which changes in gas flow rate can affect the direction of the reaction liquid flying through the air. However, making the dispersion member larger in the exhaust pipe is not desirable because it increases the pressure loss accordingly.

The present invention was devised in light of these points, and aims to provide an exhaust purification system that can suppress the effect of changes in gas flow rate on the direction of reaction liquid flow, does not require large dispersion members, and suppresses increases in pressure loss.

According to one feature of the present disclosure, an exhaust purification system is an exhaust purification system that injects a reaction liquid into an exhaust pipe of an internal combustion engine, mixes the injected reaction liquid with exhaust gas, and flows the mixture into an aftertreatment device to purify the exhaust gas, and includes the aftertreatment device, an inlet-side exhaust pipe of a predetermined length that is connected to the upstream side of the aftertreatment device and extends along the central axis of the aftertreatment device, which is the central axis of the aftertreatment device, an addition valve that is provided on the opposite side of the inlet-side exhaust pipe from the aftertreatment device and injects the reaction liquid, and a dispersion device that is disposed between the addition valve and the aftertreatment device in the inlet-side exhaust pipe and disperses the reaction liquid injected from the addition valve and mixes it with the exhaust gas, and the exhaust pipe that leads the exhaust gas from the internal combustion engine to the aftertreatment device is two exhaust pipes, a first exhaust pipe and a second exhaust pipe, on the upstream side immediately before the inlet-side exhaust pipe, and the dispersion device includes a first exhaust pipe and a second exhaust pipe on the side facing the addition valve, A collision surface is provided with which the reaction liquid injected from the addition valve collides, and the addition valve is set so that when injecting the reaction liquid, the reaction liquid is injected along the central axis of the aftertreatment device and aimed at the collision surface. The downstream end of the first exhaust pipe and the downstream end of the second exhaust pipe are each connected between the addition valve and the dispersion device in the inlet side exhaust pipe, and a first extension central axis extending from a first communication point, which is a communication point at the downstream end of the first exhaust pipe, to the central axis of the aftertreatment device intersects with the central axis of the aftertreatment device. When a virtual plane including the central axis of the aftertreatment device and the first extension central axis and an orthogonal virtual plane including the central axis of the aftertreatment device and perpendicular to the virtual plane are set, a second communication point, which is a communication point at the downstream end of the second exhaust pipe, is provided on the side of the surface opposite to the side of the first communication point in the orthogonal virtual plane.

According to this, the exhaust gas passing through the first communication point from the first exhaust pipe toward the inlet exhaust pipe and the exhaust gas passing through the second communication point from the second exhaust pipe toward the inlet exhaust pipe flow into the dispersion device along the central axis of the aftertreatment device while pushing against each other. If the flow rate of the former increases due to a change in the operating conditions, for example, the force pushing the other (the latter) increases, but at the same time, the flow rate of the latter also changes, and the force pushing the other (the former) increases. In other words, the force relationship between the two does not change before and after the change in operating conditions. Therefore, the reaction liquid injected from the addition valve travels through the exhaust gases that are pushing against each other, so it reaches the collision surface while maintaining its original direction of travel without being affected by the flow rate of the exhaust gas. Therefore, there is no need to set the size of the dispersion member in consideration of the area that the reaction liquid can reach due to changes in gas flow rate, and the dispersion member can be made smaller.

According to another feature of the present invention, in the exhaust purification system, the first exhaust pipe and the inlet exhaust pipe are integrated, and the downstream side of the first exhaust pipe is bent to form the inlet exhaust pipe.

This allows for a simpler configuration than when the first exhaust pipe and the inlet exhaust pipe are a single independent exhaust pipe, since it is only necessary to connect the downstream end of the second exhaust pipe to the inlet exhaust pipe.

According to another feature of the present invention, in the exhaust purification system, a second extension central axis extending from the second communication point to the central axis of the second exhaust pipe toward the central axis of the aftertreatment device intersects with the central axis of the aftertreatment device, and the second extension central axis is included in the imaginary plane.

With this, the exhaust gas passing from the first exhaust pipe through the first communication point toward the inlet exhaust pipe and the exhaust gas passing from the second exhaust pipe through the second communication point toward the inlet exhaust pipe merge more smoothly than when, for example, the second extension central axis is in a twisted position. Therefore, the effects of the irregular movement (turbulence, etc.) of the exhaust gas as a fluid can be suppressed, and the direction in which the reaction liquid is injected from the addition valve can be more easily set.

According to another feature of the present invention, in the exhaust purification system, the angle between the aftertreatment device central axis extending from a first intersection point, which is the intersection point between the first extension central axis and the aftertreatment device central axis, toward the aftertreatment device, and the first extension central axis extending from the first intersection point toward the downstream end of the first exhaust pipe is an obtuse angle, and the angle between the aftertreatment device central axis extending from a second intersection point, which is the intersection point between the second extension central axis and the aftertreatment device central axis, toward the aftertreatment device, and the second extension central axis extending from the second intersection point toward the downstream end of the second exhaust pipe is an obtuse angle.

With this, the exhaust gas flowing from the first exhaust pipe through the first communication point to the inlet exhaust pipe and the exhaust gas flowing from the second exhaust pipe through the second communication point to the inlet exhaust pipe merge more smoothly than when the two angles are at right angles. Therefore, the effects of the irregular movement (turbulence, etc.) of the exhaust gas as a fluid can be suppressed, and the direction in which the reaction liquid is injected from the addition valve can be set more easily.

According to another feature of the present invention, in the exhaust purification system, the first communication point and the second communication point are positioned symmetrically with respect to the orthogonal virtual plane.

This means that the mutual pushing forces of the exhaust gas passing from the first exhaust pipe through the first connecting point to the inlet exhaust pipe and the exhaust gas passing from the second exhaust pipe through the second connecting point to the inlet exhaust pipe are almost equal. Therefore, there is almost no need to consider the effects of exhaust gas, and the direction in which the reaction liquid is injected from the addition valve can be set more easily.

1 is a diagram showing an overall configuration of an internal combustion engine system equipped with an exhaust purification system of the present invention. 1 is a perspective view of a main portion of an exhaust gas purification system according to a first embodiment. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. FIG. 4 is a diagram showing the flow of exhaust gas in an inlet side exhaust pipe during low load operation. FIG. 4 is a diagram showing the flow of exhaust gas in an inlet side exhaust pipe during high load operation. FIG. 7 is a diagram showing a configuration of an exhaust pipe of an exhaust purification system according to a second embodiment. FIG. 13 is a diagram showing a configuration of an exhaust pipe of an exhaust purification system according to a third embodiment. FIG. 13 is a diagram showing a configuration of an exhaust pipe of an exhaust purification system according to a fourth embodiment. FIG. 13 is a diagram showing a configuration of an exhaust pipe of an exhaust purification system according to a fifth embodiment. FIG. 13 is a diagram showing a configuration of an exhaust pipe of an exhaust purification system according to a sixth embodiment. FIG. 1 is a diagram showing a conventional dispersion device when the exhaust gas purification system of the present invention is not provided. FIG. 13 is a diagram showing an exhaust gas purification system according to another embodiment.

The following describes an exhaust purification system 1 according to an embodiment of the present invention with reference to the drawings. The exhaust purification system 1 described in this embodiment is an example of the exhaust purification system of the present invention, and is provided in the exhaust pipe 5 of an internal combustion engine 11.

[Overall configuration of internal combustion engine system 10 (FIG. 1)]
The overall configuration of an internal combustion engine system 10 equipped with an exhaust purification system 1 according to the present invention will be described with reference to Fig. 1. Fig. 1 is a diagram showing the overall configuration of an internal combustion engine system 10 equipped with an exhaust purification system 1 according to the present invention. Note that an internal combustion engine 11 in Fig. 1 is an in-line four-cylinder diesel engine. Exhaust gas containing particulate matter (PM), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), etc. is discharged from the internal combustion engine 11. The internal combustion engine system 10 shown in Fig. 1 will be described below in order from the intake side to the exhaust side.

The intake air flow rate detection device 9a is, for example, an intake air flow rate sensor, and is provided in the intake passage 16 of the internal combustion engine 11 to output a detection signal corresponding to the flow rate of air taken in by the internal combustion engine 11 to the control device 8. The accelerator opening detection device 9b (for example, an accelerator opening sensor) outputs a detection signal corresponding to the opening of the accelerator operated by the driver (i.e., the load required by the driver) to the control device 8. The rotation detection device 9c is, for example, a rotation sensor, and outputs a detection signal corresponding to the rotation speed of the crankshaft of the internal combustion engine 11 (i.e., the engine speed) to the control device 8.

The injectors 12 to 15 are connected to fuel pipes (not shown) and are provided for each cylinder of the internal combustion engine 11, and inject a predetermined amount of fuel into each cylinder at a predetermined timing in response to a drive signal from the control device 8.

Exhaust gas from the internal combustion engine 11 is exhausted to an exhaust pipe 17 connected to the internal combustion engine 11. The exhaust gas flows downstream from the internal combustion engine 11 through the exhaust pipe 17, the integrated oxidation catalyst 7, the exhaust pipe 5, the aftertreatment device 2, and the exhaust pipe 18 in that order.

The exhaust pipe 17 is provided with a fuel addition valve 19 driven by the control device 8 and an exhaust temperature detection device 9d from the upstream side. The fuel addition valve 19 is a liquid addition valve that injects fuel (reaction liquid) into the exhaust gas to react with the exhaust gas in order to purify the exhaust gas of the internal combustion engine 11.

The integrated oxidation catalyst 7 includes an oxidation catalyst 7a, an exhaust temperature detector 9e, a DPF 7c (Diesel Particulate Filter) which is a particulate matter removal filter, and a differential pressure sensor 9h. The integrated oxidation catalyst 7 is formed in a cylindrical shape, and an oxidation catalyst 7a is provided inside. The oxidation catalyst 7a is made of a cellular cylinder formed in a cylindrical shape or the like made of ceramic, and a large number of through holes are formed in the axial direction, and the inner surface of each through hole is coated with a precious metal catalyst such as platinum (Pt). The oxidation catalyst 7a oxidizes and removes carbon monoxide (CO), hydrocarbons (HC), and the like contained in the exhaust gas by passing the exhaust gas through the large number of through holes at a predetermined temperature.

The particulate matter removal filter (hereinafter referred to as "DPF") 7c is formed into a cylindrical shape or the like from a porous member made of a ceramic material or the like. The porous DPF 7c captures particulate matter (PM) by passing the inflowing exhaust gas through it, and removes the particulate matter (PM) from the exhaust gas. As particulate matter (PM) accumulates in the DPF 7c, it becomes more difficult for the exhaust gas to pass through the DPF 7c, and the collection function decreases.

The exhaust gas temperature detection device 9d is, for example, an exhaust gas temperature sensor, and outputs a detection signal corresponding to the temperature of the exhaust gas upstream of the oxidation catalyst 7a to the control device 8. The exhaust gas temperature detection device 9e is, for example, an exhaust gas temperature sensor, and outputs a detection signal corresponding to the temperature of the exhaust gas downstream of the oxidation catalyst 7a (and upstream of the DPF 7c) to the control device 8.

The differential pressure sensor 9h outputs a detection signal to the control device 8 according to the pressure difference (pressure difference) between the exhaust pressure (exhaust pipe pressure) downstream of the oxidation catalyst 7a and upstream of the DPF 7c, and the exhaust pipe pressure downstream of the DPF 7c. Here, the pressure difference (pressure difference) changes when a large amount of particulate matter (PM) accumulates in the DPF 7c. The control device 8 can estimate, based on the detection signal output by the differential pressure sensor 9h, whether a large amount of particulate matter (PM) has accumulated in the DPF 7c, making it difficult for exhaust gas to pass through the DPF 7c, and whether it is necessary to remove the particulate matter (PM) accumulated in the DPF 7c and restore (regenerate) the DPF 7c.

When the control device 8 estimates that the DPF 7c needs to be restored (regenerated), it injects fuel (reaction liquid) into the exhaust gas from the fuel addition valve 19 in order to remove particulate matter (PM) that has accumulated in the DPF 7c. The fuel (reaction liquid) injected into the exhaust gas is mixed with the exhaust gas to form an air-fuel mixture, which flows into the integrated oxidation catalyst 7 and is guided to the inlet end surface 7b of the oxidation catalyst 7a of the integrated oxidation catalyst 7.

The fuel is oxidized by the oxygen remaining in the exhaust gas in the oxidation catalyst 7a. The heat generated by the oxidation raises the temperature of the exhaust gas, and the exhaust gas becomes hot. This hot exhaust gas raises the bed temperature of the DPF 7c, and when the bed temperature reaches a predetermined temperature or higher (for example, 590°C or higher), the particulate matter (PM) accumulated in the DPF 7c is burned and incinerated, and the collection function of the DPF 7c is restored (regenerated).

The integrated oxidation catalyst 7 is a type of exhaust purification device that receives a mixture of exhaust gas and fuel (reaction liquid) injected into the exhaust gas, causing the fuel (reaction liquid) to react with the exhaust gas.

The exhaust pipe 5 is provided between the integrated oxidation catalyst 7 and the aftertreatment device 2, and guides exhaust gas from the internal combustion engine 11 to the aftertreatment device 2. The exhaust pipe 5 has an inlet exhaust pipe 5d connected to the upstream side of the aftertreatment device 2, and two exhaust pipes, a first exhaust pipe 5b and a second exhaust pipe 5c, are provided upstream of the inlet exhaust pipe 5d. Specifically, the exhaust pipe 5 branches from the most upstream pre-branch exhaust pipe 5a connected to the integrated oxidation catalyst 7 into two exhaust pipes, a first exhaust pipe 5b and a second exhaust pipe 5c, which merge downstream to form a single inlet exhaust pipe 5d. The exhaust pipe 5 is provided with an exhaust temperature detection device 9f, a NOx sensor 9i, a urea water addition valve 3, and a dispersion device 4.

The exhaust temperature detection device 9f is, for example, an exhaust temperature sensor, and outputs a detection signal corresponding to the temperature of the exhaust gas downstream of the DPF 7c to the control device 8. The NOx sensor 9i outputs a detection signal corresponding to the concentration of NOx in the exhaust gas upstream of the selective reduction catalyst 2a to the control device 8.

The urea water addition valve (liquid addition valve) 3 is provided at the point where the first exhaust pipe 5b and the second exhaust pipe 5c join into a single inlet exhaust pipe 5d. The urea water addition valve 3 is driven by the control device 8 to inject (discharge, add) urea water (reaction liquid) 93 into the exhaust gas toward the dispersion device 4 provided upstream of the aftertreatment device 2. The urea water addition valve 3 is connected to a urea water tank 92 via a urea water supply pipe 90 and a urea water pump 91, and urea water 93 is supplied from the urea water tank 92.

The urea water pump 91 is an electric pump driven by the control device 8. A level gauge (amount detection device) 9k is provided in the urea water tank 92, which outputs a detection signal corresponding to the remaining amount (water level) of the urea water 93 stored in the urea water tank 92 to the control device 8. In addition, a concentration sensor 9m is provided in the urea water tank 92, which outputs a detection signal corresponding to the concentration of the urea water 93 stored in the urea water tank 92 to the control device 8.

The dispersion device 4 is disposed between the urea water addition valve 3 and the aftertreatment device 2 in the inlet exhaust pipe 5d. The dispersion device 4 atomizes the urea water (reaction liquid) 93 injected from the urea water addition valve 3, disperses it in the exhaust gas, and mixes it with the exhaust gas.

The aftertreatment device 2 is formed in a cylindrical shape and has a cylindrical selective reduction catalyst 2a inside. The aftertreatment device 2 is provided between the exhaust pipe 5 and the exhaust pipe 18, and is a type of exhaust purification device into which a mixture of exhaust gas and urea water (reaction liquid) 93 injected into the exhaust gas flows in, causing the urea water (reaction liquid) 93 to react with the exhaust gas.

The particulate urea water reaches the inlet end surface 2b of the selective reduction catalyst 2a from the dispersion device 4 and is reformed into ammonia by the heat of the exhaust gas. The selective reduction catalyst 2a is a catalyst that purifies the exhaust gas by reacting nitrogen oxides (NOx) in the exhaust gas with ammonia (reducing the NOx). The exhaust gas purified by the selective reduction catalyst 2a flows from the aftertreatment device 2 into the exhaust pipe 18.

The exhaust pipe 18 is connected downstream of the aftertreatment device 2, and is provided with an exhaust temperature detection device 9g and a NOx sensor 9j. The exhaust temperature detection device 9g is, for example, an exhaust temperature sensor, and outputs a detection signal corresponding to the temperature of the exhaust gas downstream of the aftertreatment device 2 to the control device 8. The NOx sensor 9j outputs a detection signal corresponding to the concentration of NOx in the exhaust gas downstream of the aftertreatment device 2 to the control device 8.

The control device 8 is a known device equipped with a CPU, RAM, ROM, timer, EEPROM, etc. The CPU executes various calculation processes based on various programs and maps stored in the ROM. The RAM also temporarily stores the results of calculations by the CPU and data input from each detection device, and the EEPROM stores, for example, data that should be saved when the internal combustion engine 11 is stopped.

The control device 8 can then detect the operating state of the internal combustion engine 11 based on the input detection signal. The control device 8 also outputs control signals to control the amount of fuel injected from each injector 12-15 into the cylinder of the internal combustion engine 11, the amount of unburned fuel added (injected) from the fuel addition valve 19, and the amount of urea water added (injected) from the urea water addition valve 3, in response to the detected operating state of the internal combustion engine 11 and a request from the driver based on the detection signal from the accelerator opening detection device 9b.

[Exhaust gas purification system 1 according to the first embodiment (FIGS. 2 to 4)]
Next, the configuration of the exhaust purification system 1 will be described with reference to Figures 2 to 4. Figure 2 is a perspective view of a main part of the exhaust purification system 1 according to the first embodiment. Figure 3 is a cross-sectional view taken along line III-III in Figure 2. Figure 4 is a cross-sectional view taken along line IV-IV in Figure 2.

As shown in FIG. 2, the exhaust purification system 1 has an aftertreatment device 2 and an inlet exhaust pipe 5d with a length L that is connected to the upstream side of the aftertreatment device 2 and extends along the central axis 2c of the aftertreatment device. As shown in FIG. 3, the exhaust purification system 1 has a urea water addition valve 3 and a dispersion device 4 in the inlet exhaust pipe 5d. The urea water addition valve 3 is provided on the opposite side of the inlet exhaust pipe 5d from the aftertreatment device 2, and injects urea water 93 toward the dispersion device 4. The dispersion device 4 is disposed between the urea water addition valve 3 and the aftertreatment device 2 in the inlet exhaust pipe 5d, and disperses the urea water 93 injected from the urea water addition valve 3 and mixes it with the exhaust gas.

2, the exhaust pipe 5 guides exhaust gas from the internal combustion engine 11 to the aftertreatment device 2. The exhaust pipe 5 is, for example, a single exhaust pipe 5e (the pre-branch exhaust pipe 5a, the first exhaust pipe 5b, and the second exhaust pipe 5c are integrated) bent at the upstream and downstream sides, to which the second exhaust pipe 5c is connected by welding or the like. As a result, on the upstream side immediately before the inlet exhaust pipe 5d, there are two exhaust pipes, the first exhaust pipe 5b and the second exhaust pipe 5c. The downstream ends of the first exhaust pipe 5b and the second exhaust pipe 5c are connected between the urea water addition valve 3 and the dispersion device 4 in the inlet exhaust pipe 5d. Note that the exhaust pipes 5a to 5d may each be a single independent exhaust pipe. In that case, the exhaust pipe 5 is formed by connecting the exhaust pipes 5a to 5d by welding or the like.

The first communication point 6a is where the downstream end of the first exhaust pipe 5b communicates with the inlet exhaust pipe 5d. The second communication point 6b is where the downstream end of the second exhaust pipe 5c communicates with the inlet exhaust pipe 5d. In addition to these communication points 6a and 6b, by considering various imaginary lines and planes, the configuration of the exhaust pipes 5b, 5c, and 5d, the positional relationship determined between the downstream ends of the exhaust pipes 5b and 5c and the inlet exhaust pipe 5d, and the positional relationship determined between the downstream end of the first exhaust pipe 5b and the downstream end of the second exhaust pipe 5c, etc. are explained.

For example, the first extension central axis 6x is an imaginary line extending the central axis 5x of the first exhaust pipe 5b from the first communication point 6a toward the aftertreatment device central axis 2c. When considering such a first extension central axis 6x, the first extension central axis 6x and the aftertreatment device central axis 2c intersect. The intersection point P is the intersection point of the first extension central axis 6x and the aftertreatment device central axis 2c.

For example, the imaginary plane S1 is an imaginary plane that includes the post-processing device central axis 2c and the first extended central axis 6x. The imaginary plane S2 is an imaginary plane that includes the post-processing device central axis 2c and is perpendicular to the imaginary plane S1. When considering such imaginary planes S1 and S2, the second communication point 6b is provided on the side opposite the side of the imaginary plane S2 that faces the first communication point 6a. In addition, the first communication point 6a and the second communication point 6b are positioned symmetrically with respect to the imaginary plane S2.

For example, the second extension central axis 6y is an imaginary line extending the central axis 5y of the second exhaust pipe 5c from the second communication point 6b toward the aftertreatment device central axis 2c. When considering such a second extension central axis 6y, the second extension central axis 6y intersects with the aftertreatment device central axis 2c at the intersection point P. In addition, the second extension central axis 6y, the first extension central axis 6x, and the aftertreatment device central axis 2c are on the same plane (imaginary plane S1).

θ1 is the angle between the post-processing device central axis 2c and the first extended central axis 6x. θ2 is the angle between the post-processing device central axis 2c and the second extended central axis 6y. θ1 and θ2 are both obtuse angles.

As shown in Figures 3 and 4, the dispersion device 4 has a cylinder 4a and dispersion plates 4b to 4d. The cylinder 4a is cylindrical, and its outer peripheral surface is fixed along the inner peripheral surface of the inlet exhaust pipe 5d. The dispersion plates 4b to 4d are plate-shaped, and are provided in the same number as the nozzle holes of the urea water addition valve 3, for example. One end of the dispersion plates 4b to 4d is fixed to the inner peripheral surface of the cylinder 4a, and the other end has collision surfaces 4x to 4z. The collision surfaces 4x to 4z are part of the dispersion plates 4b to 4d, and the urea water sprayed from the urea water addition valve 3 collides against them.

As shown in FIG. 3, the urea water addition valve 3 is provided in the inlet exhaust pipe 5d along the central axis 2c of the aftertreatment device. The urea water addition valve 3 has three nozzle holes corresponding to the dispersion plates 4b to 4d. The direction of the urea water addition valve 3 is set so that each nozzle hole sprays urea water aiming at the impact surfaces 4x to 4z of the corresponding dispersion plates 4b to 4d.

As shown in Figures 2 and 3, the inside diameters of exhaust pipes 5e and 5c are the same. The exhaust gas flowing through pre-branch exhaust pipe 5a flows into first exhaust pipe 5b and second exhaust pipe 5c at approximately the same flow rate. The exhaust gas flowing into exhaust pipes 5b and 5c joins at inlet exhaust pipe 5d, passes through dispersion device 4, and flows into post-treatment device 2.

[Regarding the effects of the exhaust gas purification system 1 according to the first embodiment (FIGS. 5 and 6)]
FIG. 5 is a diagram showing the flow of exhaust gas in the inlet exhaust pipe during low load operation. For example, when the internal combustion engine 11 is operating at low load, such as during idling, the exhaust gases with low flow rates merge together. FIG. 6 is a diagram showing the flow of exhaust gas in the inlet exhaust pipe during high load operation. For example, when the internal combustion engine 11 is operating at high load, such as during acceleration, the exhaust gases with high flow rates merge together. The arrows shown in FIGS. 5 and 6 indicate the flow of exhaust gas flowing through the exhaust pipes 5b to 5d. The length of each arrow indicates the flow rate, and the longer the arrow, the greater the exhaust gas flow rate.

As shown in FIG. 5, the exhaust gas flowing through the first exhaust pipe 5b passes through the first communication point 6a and heads toward the inlet exhaust pipe 5d. Similarly, the exhaust gas flowing through the second exhaust pipe 5c passes through the second communication point 6b and heads toward the inlet exhaust pipe 5d. Because the two exhaust pipes 5b and 5c, which have the same inner diameter, branch from the pre-branch exhaust pipe 5a (see FIG. 1), the flow rates of both are approximately equal. Therefore, the two pipes push against each other with approximately the same force relationship as they flow into the dispersion device 4 along the central axis 2c of the aftertreatment device.

As shown in Figure 6, when the driving conditions change, for example, from idling to accelerating, the flow rates of both increase. However, there is no difference between the two, and the flow rates are almost equal. Therefore, both flow into the dispersion device 4 along the central axis 2c of the post-treatment device, pushing against each other with almost the same force relationship.

As shown in FIG. 4, the urea water injected from the urea water addition valve 3 reaches areas 4g-4i on the collision surfaces 4x-4z, for example, during idling. On the other hand, even during acceleration, the urea water injected from the urea water addition valve 3 travels through the exhaust gases that are pushing against each other, and so reaches areas 4j-4m near areas 4g-4i without being affected by changes in the exhaust gas flow rate. In this way, by suppressing the effect of changes in the exhaust gas flow rate on the traveling direction of the injected urea water, it is possible to reduce the size of the collision surfaces 4x-4z compared to conventional methods.

Figure 12 is a diagram showing a conventional dispersion device 80 that does not include the exhaust purification system of the present invention. For example, during idling, the collision surfaces 81-83 reach areas 84-86. On the other hand, during acceleration, the urea water injected from the urea water addition valve 3 is pushed by the exhaust gas with an increased flow rate and changes direction, so it reaches areas 87-89, which are far away from areas 84-86. In this way, if the exhaust gases do not push against each other, the urea water injected from the urea water addition valve 3 is directly affected by the flow rate of the exhaust gas flowing from the first exhaust pipe 5b to the inlet exhaust pipe 5d. For this reason, it was necessary to set the collision surfaces 81-83 in the dispersion device 80 to be large.

[Exhaust gas purification system 21 according to a second embodiment (FIG. 7)]
Next, an exhaust gas purification system 21 according to a second embodiment of the present invention will be described. Note that the description of the matters already described in the first embodiment will be omitted as appropriate.

As shown in FIG. 7, in the exhaust purification system 21, the exhaust pipe 17 is branched into a first exhaust pipe 22 and a second exhaust pipe 23 midway, unlike the first embodiment. Even in this way, two exhaust pipes, the first exhaust pipe 22 and the second exhaust pipe 23, can be formed on the upstream side immediately before the inlet exhaust pipe 5d. The first exhaust pipe 22 and the second exhaust pipe 23 are provided with an oxidation catalyst 7a and a DPF 7c, respectively. The urea water addition valve 3 is provided on the opposite side of the aftertreatment device 2 in the inlet exhaust pipe 5d where the first exhaust pipe 22 and the second exhaust pipe 23 join. The downstream ends of the first exhaust pipe 22 and the second exhaust pipe 23 are connected between the urea water addition valve 3 and the dispersion device 4 in the inlet exhaust pipe 5d.

The first exhaust pipe 22 is formed by connecting, for example, a single exhaust pipe 24 (the exhaust pipe 17, the first exhaust pipe 22, and the inlet exhaust pipe 5d are integrated) whose upstream and downstream sides are bent, to a separate second exhaust pipe 23 by welding or the like. Note that the first exhaust pipe 22 may be formed by connecting independent exhaust pipes 17, 22, 23, and 5d by welding or the like.

[Third embodiment of exhaust gas purification system 31 (FIG. 8)]
Next, an exhaust gas purification system 31 according to a third embodiment of the present invention will be described. Note that the description of the matters already described in the first and second embodiments will be omitted as appropriate.

As shown in FIG. 8, in the exhaust purification system 31, exhaust gas from cylinders 32 and 33 in the internal combustion engine 11 is exhausted to a first exhaust pipe 36, and exhaust gas from cylinders 34 and 35 is exhausted to a second exhaust pipe 37. In an in-line four-cylinder internal combustion engine 11, the exhaust stroke is performed in the order of cylinder 32, cylinder 35, cylinder 33, and cylinder 34, so the flow rate of exhaust gas in the first exhaust pipe 36 and the second exhaust pipe 37 is equal. Even in this way, two exhaust pipes, the first exhaust pipe 36 and the second exhaust pipe 37, can be used upstream just before the inlet exhaust pipe 5d.

[Fourth embodiment of exhaust gas purification system 41 (FIG. 9)]
Next, an exhaust gas purification system 41 according to a fourth embodiment of the present invention will be described. Note that the description of the matters already described in the first to third embodiments will be omitted as appropriate.

As shown in FIG. 9, the exhaust purification system 41 has an inlet exhaust pipe 42 connected to the upstream side of the integrated oxidation catalyst 7, and immediately upstream of the inlet exhaust pipe 42, there are two exhaust pipes, a first exhaust pipe 36 and a second exhaust pipe 37. Exhaust gas from cylinders 32 and 33 in the internal combustion engine 11 is exhausted to the first exhaust pipe 36, and exhaust gas from cylinders 34 and 35 is exhausted to the second exhaust pipe 37. The first exhaust pipe 36 and the second exhaust pipe 37 only allow exhaust gas to flow downstream, and are not provided with an oxidation catalyst 7a and a DPF 7c.

The configuration of exhaust pipes 36, 37, 42, the positional relationship established between the downstream ends of exhaust pipes 36, 37 and the inlet side exhaust pipe 42, the positional relationship established between the downstream end of first exhaust pipe 36 and the downstream end of second exhaust pipe 37, etc. are similar to the configuration of exhaust pipes 5b, 5c, 5d, the positional relationship established between the downstream ends of exhaust pipes 5b, 5c and the inlet side exhaust pipe 5d, the positional relationship established between the downstream end of first exhaust pipe 5b and the downstream end of second exhaust pipe 5c, etc.

The fuel addition valve 19 is provided on the opposite side of the inlet exhaust pipe 42 from the integrated oxidation catalyst 7 and injects fuel. The dispersion device 43 is disposed between the fuel addition valve 19 and the integrated oxidation catalyst 7 in the inlet exhaust pipe 42. The dispersion device 43 is provided with a collision surface (see FIG. 4) on the side facing the fuel addition valve 19 against which the fuel injected from the fuel addition valve 19 collides. When injecting fuel, the fuel addition valve 19 is set to inject fuel along the central axis (see FIG. 2) of the integrated oxidation catalyst 7 and aimed at the collision surface of the dispersion device 43.

[Exhaust gas purification system 51 according to a fifth embodiment (FIG. 10)]
Next, an exhaust gas purification system 51 according to a fifth embodiment of the present invention will be described. Note that the description of the matters already described in the first to fourth embodiments will be omitted as appropriate.

10, in an exhaust purification system 51, in a V6 internal combustion engine 52, exhaust gas from cylinders in a left bank 53 is exhausted to a first exhaust pipe 55, and exhaust gas from cylinders in a right bank 54 is exhausted to a second exhaust pipe 56. Even in this manner, two exhaust pipes, the first exhaust pipe 55 and the second exhaust pipe 56, can be provided on the upstream side immediately before the inlet side exhaust pipe 5d.
[Exhaust gas purification system 61 according to a sixth embodiment (FIG. 11)]
Next, an exhaust gas purification system 61 according to a sixth embodiment of the present invention will be described. Note that the description of the matters already described in the first to fifth embodiments will be omitted as appropriate.

As shown in FIG. 11, the exhaust purification system 61 has an inlet exhaust pipe 64 connected to the upstream side of the integrated oxidation catalyst 7, and immediately upstream of the inlet exhaust pipe 64, there are two exhaust pipes, a first exhaust pipe 62 and a second exhaust pipe 63. In the V-type 6-cylinder internal combustion engine 52, exhaust gas from the cylinders of the left bank 53 is exhausted to the first exhaust pipe 62, and exhaust gas from the cylinders of the right bank 54 is exhausted to the second exhaust pipe 63.

The fuel addition valve 19 is provided on the opposite side of the inlet exhaust pipe 64 from the integrated oxidation catalyst 7 and injects fuel. The dispersion device 65 is disposed between the fuel addition valve 19 and the integrated oxidation catalyst 7 in the inlet exhaust pipe 42. The dispersion device 43 is provided with a collision surface (see FIG. 4) on the side facing the fuel addition valve 19 against which the fuel injected from the fuel addition valve 19 collides. When injecting fuel, the fuel addition valve 19 is set to inject fuel along the central axis (see FIG. 2) of the integrated oxidation catalyst 7 and aimed at the collision surface of the dispersion device 66.

The exhaust purification system of the present invention is not limited to the appearance, configuration, structure, etc. described in this embodiment, and various modifications, additions, and deletions are possible without changing the gist of the present invention. For example, in the first embodiment, a second exhaust pipe 5c is connected to one exhaust pipe 5e by welding or the like. However, for example, as in the exhaust purification system 71 shown in FIG. 13, a first exhaust pipe 72 and a second exhaust pipe 73 may be connected to an inlet exhaust pipe 74 by welding or the like.

In the first embodiment, the first exhaust pipe 5b and the second exhaust pipe 5c are described as having the same inner diameter, but the inner diameters of the two may be different. For example, as shown in FIG. 13, the inner diameter r2 of the second exhaust pipe 73 may be set smaller than the inner diameter r1 of the first exhaust pipe 72.

In the first embodiment, the positional relationship between the first communication point 6a and the second communication point 6b has been described as being symmetrical with respect to the virtual plane S2. However, the second communication point 6b only needs to be provided on the side opposite to the side of the first communication point 6a in the virtual plane S2. For example, as shown in FIG. 13, the second communication point 76 may be shifted downstream of the inlet exhaust pipe 74. As a result, the second extension central axis 6y does not pass through the intersection point P. The intersection point 77 is the intersection point of the second extension central axis 6y and the post-treatment device central axis 2c. Furthermore, the second extension central axis 6y may not be on the virtual plane S1 and may be in a twisted position with respect to the first extension central axis 6x or the post-treatment device central axis 2c. However, in any case, the second communication point 76 must be located between the urea water addition valve 3 and the dispersion device 4 in the inlet exhaust pipe 5d.

1, 21, 31, 41, 51, 61 Exhaust gas purification system 2 Aftertreatment device 2a Selective reduction catalyst 2b Inflow side end surface 2c Aftertreatment device central axis 3 Urea water addition valve 4 Dispersion device 4a Cylinder 4b-4d Dispersion plate 4x-4z Collision surface 5 Exhaust pipe 5a Pre-branch exhaust pipe 5b First exhaust pipe 5c Second exhaust pipe 5d Inflow side exhaust pipe 5x First exhaust pipe central axis 5y Second exhaust pipe central axis 6a First communication point 6b Second communication point 6x First extension central axis 6y Second extension central axis 7 Integrated oxidation catalyst 7a Oxidation catalyst 7b Inflow side end surface 7c DPF
8 Control device 9a Intake air flow rate detection device 9b Accelerator opening detection device 9c Revolution detection device 9d to 9g Exhaust temperature detection device 9h Differential pressure sensor 9i, 9j NOx sensor 9k Level gauge 9m Concentration sensor 10 Internal combustion engine system 11 Internal combustion engine 12 to 15 Injector 16 Intake passage 17, 18 Exhaust pipe 19 Fuel addition valve 90 Urea water supply pipe 91 Urea water pump 92 Urea water tank 93 Urea water

Claims (4)

An exhaust purification system that injects a reaction liquid into an exhaust pipe of an internal combustion engine, mixes the injected reaction liquid with exhaust gas, and causes the exhaust gas to flow into an aftertreatment device to purify the exhaust gas,
The exhaust purification system includes:
The post-treatment device;
an inlet-side exhaust pipe having a predetermined length, the inlet-side exhaust pipe being connected to the upstream side of the aftertreatment device and extending along a central axis of the aftertreatment device, the central axis of the aftertreatment device being the central axis of the aftertreatment device;
an addition valve that is provided on the inlet side exhaust pipe on the opposite side to the aftertreatment device and that injects the reaction liquid;
a dispersion device disposed between the addition valve and the aftertreatment device in the inlet-side exhaust pipe to disperse the reaction liquid injected from the addition valve and mix it with the exhaust gas;
It has
an exhaust pipe that guides exhaust gas from the internal combustion engine to the aftertreatment device includes two exhaust pipes, a first exhaust pipe and a second exhaust pipe, on an upstream side immediately before the inlet-side exhaust pipe;
the dispersion device is provided with a collision surface on a side facing the addition valve against which the reaction liquid sprayed from the addition valve collides,
the addition valve is set so as to inject the reaction liquid along a central axis of the post-treatment device and to inject the reaction liquid toward the collision surface,
a downstream end of the first exhaust pipe and a downstream end of the second exhaust pipe are each connected between the addition valve and the dispersion device in the inlet side exhaust pipe,
a first extension central axis, which is an extension of a central axis of the first exhaust pipe from a first communication point, which is a communication point at a downstream end of the first exhaust pipe, toward a central axis of the aftertreatment device, intersects with the central axis of the aftertreatment device,
when a virtual plane including the central axis of the aftertreatment device and the first extension central axis and an orthogonal virtual plane including the central axis of the aftertreatment device and perpendicular to the virtual plane are set, a second communication point which is a communication point of a downstream end of the second exhaust pipe is provided on a surface opposite to a surface on a side of the first communication point in the orthogonal virtual plane,
The first exhaust pipe and the inlet-side exhaust pipe are integrated together, and a downstream side of the first exhaust pipe is bent to form the inlet-side exhaust pipe.
Exhaust purification system. 2. The exhaust purification system according to claim 1 ,
a second extension central axis, which is obtained by extending a central axis of the second exhaust pipe from the second communication point toward a central axis of the aftertreatment device, intersects with the central axis of the aftertreatment device,
The second extension central axis is included in the imaginary plane.
Exhaust purification system. 3. The exhaust gas purification system according to claim 2 ,
an angle formed by the aftertreatment device central axis line extending from a first intersection point, which is an intersection point between the first extension central axis line and the aftertreatment device central axis line, toward the aftertreatment device, and the first extension central axis line extending from the first intersection point toward a downstream end of the first exhaust pipe, is an obtuse angle,
an angle formed by the aftertreatment device central axis line extending from a second intersection point, which is an intersection point between the second extension central axis line and the aftertreatment device central axis line, toward the aftertreatment device, and the second extension central axis line extending from the second intersection point toward the downstream end of the second exhaust pipe, is an obtuse angle;
Exhaust purification system. The exhaust gas purification system according to any one of claims 1 to 3 ,
The first communication point and the second communication point are positioned symmetrically with respect to the orthogonal virtual plane.
Exhaust purification system.

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